Potassium superoxide is a product particularly well suited for the regeneration of a breathable atmosphere because it has the characteristic of fixing carbon dioxide gas and water vapor and releasing oxygen according to the reactions: ##EQU1## This characteristic is used to make atmosphere regenerators having closed chambers and respiratory apparatus which operate in a closed circuit.
Breathing apparatus essentially consist of a cartridge, for example a metal box, in which the superoxide is placed, and a lung bag, these two elements being connected to each other and to the user of the apparatus in such a way that the exhaled gas goes through the superoxide leaving there most of the carbon dioxide gas and a large part of the water vapor, whereby this becomes enriched with oxygen; this gas is stored in the lung bag from which the user inhales the regenerated air.
As this apparatus must be carried by the user, the best compromise between total weight of the apparatus and endurance must be obtained. For a given respiratory level, this compromise is all the more difficult to achieve the shorter the endurance of the apparatus and, consequently, the lower the potassium superoxide charge. Actually, when the carrier of the apparatus makes a sustained effort, corresponding to a work of 100 to 200 watts, for example, the biological consumption of oxygen is between 1.2 and 1.5 l/min. and the CO.sub.2 rejected is between 1 and 1.35 l/min. for a respiratory quotient of 0.90. The respiratory output is between 30 and 35 l/min.
When the superoxide charge decreases, the reactive level imposed on the charge increases and the utilization rate of the superoxide tends then to decrease, unless its reactivity is increased; but the reactivity is limited, on the one hand, by the reaction of the superoxide to temperature and, on the other hand, by chemical exchanges between the gas and the superoxide.
An apparatus is generally designed to meet the respiratory needs of a man performing a given level of effort for a well determined period.
Therefore, for each apparatus, the minimum weight of superoxide corresponding to a maximum utilization rate is sought, which involves correlating as well as possible the following parameters: reactivity of the superoxide, its reaction to temperature, thickness and shape of superoxide pellets and structure of the superoxide charge.
If it is desired to keep the weight and the dimensions of the apparatus within tolerable limits, it is necessary that the superoxide charge be used as completely as possible, yet without the content of CO.sub.2 of the gas inhaled exceeding 1.5% or the pressure to be exerted upon exhalation becoming greater than 6.5 millibars.
Several partial solutions have been suggested and even used in existing rebreathing devices. To obtain the best efficiency for oxygen generation, a catalyst is added, as for example, a cation that derives from transition metals, generally the cation CU.sup.++.
No matter what the method of manufacturing the potassium superoxide, it is first transformed into very fine powder form. According to one process, some metallic potassium is burned in a chamber containing superoxygenated air; then KO.sub.2 in the form of very light flakes is obtained which are then brought together, after adding the catalyst, in fragments of rather hetergeneous compositions, sizes and shapes.
In the process described in French Pat. No. 2,175,652, hydrogen peroxide and potash are made to react to provide a peroxide solution on which a dismutation is performed on the warm outer surface of a horizontal cylinder, turning around its axis; then the potassium superoxide is collected in the form of flakes by scraping the surface of the cylinder. The product thus manufactured contains about 80 to 85% KO.sub.2, 12 to 15% KOH, 2 to 5% H.sub.2 O. After adding copperoxychloride, it is very easily put in the shape of pellets by processing in a rotating compression machine, which makes possible a packaging of the particles with a homogeneous and rigorous controlled porosity, composition and shape.
However, these various agglomeration processes are not sufficient to assure, in the case of intensive use of the regenerating charge, a stability or a sufficiently low increase of the pressure drop at exhalation, which is compatible with prolonged use of the breathing apparatus and a high utilization rate of the potassium superoxide.
Actually, the strong exothermic nature of the reactions (1) and (2) induce considerable heating within the KO.sub.2 charge. In the heart of the regenerating charge, the pellets or agglomerates become destroyed and transformed into a more or less viscous bulk which resists the passage of the gas by clogging passageways therethrough, creating a very considerable rise in the pressure drop; alternatively preferential paths are formed which reduce the rate of fixation of CO.sub.2 whose content in the inhaled gas too quickly becomes greater than the tolerable threshold.
An effort has been made to eliminate these drawbacks by giving the cartridge such a structure that the gas goes through only a small thickness of superoxide at low speed, or by separating the charge into small fractions by metal partitions which come in contact with the wall and thus, have a heat exchange function; thus, complex structures result in which the weight of non-reactive matter is relatively significant. These complex structures have a high production cost and filling them is rather difficult and does not lend itself well to automation.